This invention relates to production of amino acids using auxotrophic mutants of a methylotrophic Bacillus.
Microorganisms that utilize one-carbon compounds more reduced than carbon dioxide (methylotrophs) are diverse and ubiquitous. Anthony, The Biochemistry of methylotrophs, p 3 (Academic Press, London 1982); Hanson, Adv. Appl. Microbiol., 26:3 (1980). Those methylotrophic bacteria reported to utilize methane are all gram-negative and nearly all have an obligate requirement for one-carbon compounds as energy sources (Anthony, supra; Whittenburg et al. J Gen. Microbiol. 61: 219-226 (1970)). Bacteria that grow on methanol and methylamines but not methane include several facultative as well as obligate methylotrophs (Anthony, supra; Hanson, supra. All the obligate methylotrophs unable to utilize methane are gram-negative aerobic bacteria (Anthony, supra.; Whittenburg, supra). Of the facultative methylotrophs isolated that utilize methanol, methylamine or both, only a few were gram positive and were assigned to the genera Bacillus, Corynebacterium, Arthrobacter, or Nocardia (Akiba et al, J. Ferment. Technol., 48:323-328 (1970); Clement et al. Abstracts of the Fifth International Symposium Microbiol. Growth on C.sub.1 Compounds, p. 69 (Free Univ. Press, Amsterdam 1986); Hazen et al, Arch. Microbiol., 135: 205-210 (1983); Mimura et al., J. Ferment. Technol., 56: 243-252 (1978).
Production of single cell protein and selected amino acids by microbial fermentation is known, e.g., U.S. Pat. No. 4,652,527 to Stirling. One amino acid which has been produced on an industrial scale is lysine, see Tosaka et al., Trends in Biotechnology, 1: 70-74 (1983), Tosaka and Takinami, Progress in Industrial Microbiology, Ch. 24, p. 152-172 (Aida et al., 1986). Bacillus species have been used in fermentation processes to produce amino acids, Tosaka et al., supra.; Tosaka and Takinami, supra. However, to date no production of amino acids using an isolated Bacillus species capable of rapid growth on methanol at temperatures above 50.degree. C. has occurred.
The industrial advantages of a thermophilic methanol utilizing fermentation process at elevated temperatures have been described, Snedecor and Cooney, Appl. Microbiol., 27: 112-1117 (1974). For example, use of elevated temperatures can significantly reduce cooling costs. A methanol utilizing, thermophilic mixed culture that included an endosporeforming species was selected by Snedecor and Cooney; however, Snedecor and Cooney, were unable to isolate a pure culture capable of growth on methanol. It is extremely difficult or impossible to isolate appropriate mutants from mixed or impure cultures.
Accordingly, there is a need for a method of producing amino acids using a type I methylotrophic bacterium of the genus Bacillus which exhibits sustained growth at 50.degree. C. in medium having a nitrogen source, vitamin B.sub.12 and methanol as a source of carbon and energy.